1. Field
The present disclosure relates generally to communication systems, and more particularly, to concepts and techniques for canceling narrow-band interference in a wireless receiver.
2. Background
In a wireless communications system, a transmitter typically processes (e.g., encodes and modulates) data and generates a radio frequency (RF) modulated signal. The transmitter then transmits the modulated signal through a wireless medium to a receiver. As the modulated signal propagates through the wireless medium, it may be subject to noise, interference, and other disturbances.
The function of the receiver is to recover the modulated signal in the presence of these disturbances. The design of the receiver will depend not only on the type of signal to be detected, but the nature of the disturbances. Narrow-band interference, for example, is a type of disturbance that can present unique challenges for a receiver designer. Unless properly filtered, the receiver may be unable to recover the modulated signal.
Narrow-band interference is often a concern in broadcast systems. These systems often operate in the UHF region, and therefore, are susceptible to narrow-band interference from TV signals operating in the same region of the frequency spectrum. Another source of narrow-band interference is other channels, whose interaction due to the non-linearity of the receiver may result in equivalent in-band components. The most common effects in this category are IM2 and IM3 interferers. The second-order non-linearity (IM2) components are generally out of band, except for a DC component which can be cancelled by a DC offset. The IM3 imperfections, however, tend to produce in-band components that can appear anywhere in the baseband signal, depending on the frequency of the narrow-band interference.
There is therefore a need in the art for techniques to cancel narrow-band interference at a wireless receiver.